Like COLLECTS, I have changed sight blades from what they came with to accommodate my gun, chosen load and eyesight. With my 5 inch Model 27-2, when sighted in for 125 grain JHP .357 ammo at 25 yards, the sight was cranked way up, leaving little of the threads holding it in place. I put in a taller blade which let me crank the sight body back down to where it was more secure from being bumped. I think I had to swap out the blade in my Model 25-5 4 incher to get a POA/POI at 25 yards with factory 250-255 grain lead bullet factory ammo, too.